Generally, an electric vehicle has a back-up battery therein. Moreover, a vehicle is provided therein with a vehicle auxiliary electric-power-supplying system that converts high-voltage power supplied from an overhead wire, to low-voltage power, and supplies the low-voltage power to a load installed in the vehicle. Only when electric power has been supplied from the back-up battery voltage to a controller of the vehicle auxiliary electric-power-supplying system, and the controller has operated, the entire vehicle auxiliary electric-power-supplying system has become ready to start. However, when voltage of the back-up battery decreases and does not reach enough voltage to operate the controller, the controller does not start to operate, resultantly the entire vehicle-auxiliary-electric-power-supplying- system does not operate.
Therefore, as disclosed, for example, in FIG. 1 and FIG. 2 of Japanese Laid-Open Patent Publication 259,704/1989, an electric power supplier (converter) has been provided for converting the high-voltage power, which is supplied from the overhead wire, to the low-voltage power, and supplying the electric power (electric power source) to the controller (control circuit), when the vehicle auxiliary electric-power-supplying system starts to operate. In response to the operation of the power supplier, when the vehicle starts to operate, even though the voltage of the back-up battery has decreased, the controller in the vehicle auxiliary electric-power-supplying system normally operates with electric power being supplied from the power supplier.
However, in the above described vehicle auxiliary electric-power-supplying system, there has been the following problem. The power supplier, in order to reduce its frequency in use, operates only when the vehicle auxiliary electric-power-supplying system starts to operate, then the operation is stopped after electric power has been obtained from output of an electric power inverter. If any short-circuit malfunction occurs during the starter stop, due to an affect such as a dielectric breakdown on the low-voltage side between the electric power inverter and the load, in order to stop the output from the electric power inverter, the controller needs to command the electric power inverter to stop operation. However, because normal electric power from the electric power inverter cannot be obtained due to short-circuit, and in addition, the power supplier is also stopped, the power for the controller is stopped; consequently, a normally stopping operation of the electric power inverter based on the command from the controller has been impossible.
An objective of the present invention, which has been made to solve the foregoing problem, is to obtain a vehicle auxiliary electric-power-supplying system that can suppress the frequency in use for a power supplier as low as possible, and can normally stop an electric power inverter by the power supplier being immediately started to supply electric power to a controller, even in a case in which normal electric power has become unable to be obtained from the output of the electric power inverter.